1. Field of Invention
The present invention relates, generally, to automotive powertrain systems and, more specifically, to an electric drive unit for a powertrain system.
2. Description of the Related Art
Conventional automotive vehicles known in the art include a powertrain system in rotational communication with one or more drivelines. Typically, the vehicle includes a pair of drivelines, each defined by a respective pair of opposing wheels. The powertrain system includes a propulsion system adapted to generate and selectively translate rotational torque to one or more of the wheels so as to drive the vehicle. To that end, in conventional automotive powertrain systems, the propulsion system is typically realized as an internal combustion engine in rotational communication with a transmission. The engine generates rotational torque which is selectively translated to the transmission which, in turn, translates rotational torque to one or more of the drivelines. The transmission multiplies the rotational speed and torque generated by the engine through a series of predetermined gear sets, whereby changing between gear sets enables the vehicle to travel at different vehicle speeds for a given engine speed.
In order to achieve increased fuel economy and improved engine emissions, so-called “hybrid vehicle technology” has been increasingly used in powertrain systems known in the related art. In a hybrid vehicle, the propulsion system typically includes both a gas-powered internal combustion engine as well as a battery-powered electric motor, both of which cooperate with the transmission to generate and translate rotational torque to one or both vehicle drivelines. Such a hybrid vehicle propulsion system is configured to optimize the efficiency of the engine and motor, respectively, so as to minimize fuel consumption and engine emissions. In addition, the electric motor is frequently also used as a generator during vehicle braking to charge the battery, thereby further increasing efficiency and vehicle range.
With the advent of improved electric motor and battery technology, automotive vehicles in the related art also frequently include propulsion systems that omit an internal combustion engine altogether. So-called “electric vehicle” propulsion systems typically include a large electric motor in rotational communication with a transmission and/or differential which, in turn, is used to translate rotational torque to the wheels of one or both of the drivelines. Alternatively, in other types of electric vehicle powertrain systems, smaller individual electric motors are allocated to each of the driven wheels of the vehicle. Despite the increasing efficiency of electric propulsion systems in the related art, problems associated with limited driving distance and long battery charging time present barriers to widespread industry implementation of electric propulsion technology. One solution involves outfitting the electric vehicle with a “range extender,” which is typically realized as a small internal combustion engine that serves purely as an electric generator and that is not in rotational communication with the propulsion system. However, implementation of a range extender is not always feasible in certain applications where vehicle weight, component packaging, and zero-emissions requirements are critical.
Each of the components and systems of the type described above must cooperate to effectively modulate translation of rotational torque to the driven wheels of the vehicle. In addition, each of the components and systems must be designed not only to facilitate improved performance and efficiency, but also so as to reduce the cost and complexity of manufacturing vehicles. While powertrain propulsion systems known in the related art have generally performed well for their intended use, there remains a need in the art for a propulsion system that has superior operational characteristics, a reduced overall packaging size, reduced parasitic losses, increased efficiency and, at the same time, that reduces the cost and complexity of manufacturing vehicles.